1. Field of Invention
This invention pertains to the field of medical devices and particularly to medical devices for insertion into and prolonged use in animals.
2. Description of the Background Art
Skin exit site infections are a major source of morbidity with all indwelling intra-abdominal and intravascular medical devices such as catheters. Made from a flexible polymeric material, such as silicone or polyurethane, these catheters, while being biocompatible, are associated with infections at the site where they exit from the skin. Despite attempts to minimize the risk of infection by the use of different techniques of catheter placement and modification of catheter design, exit site infections continue to be a problem with catheters indwelling for any prolonged period of time.
Since the skin is an efficient barrier to infection, it is not surprising that a break therein would lead to bacterial entry, especially of staphylococcus, streptococcus, and gram negative organisms. It is, therefore, curious to note that disruption of this barrier by teeth and horns is not associated with recurrent infection. Since hydroxylapatite (HA), the mineral component of teeth and horns, is known to be a bioactive ceramic, a skin-HA interface would possess properties that would minimize bacterial entry and infection.
An hydroxylapatite device comprising a rigid cylindrical portion coaxially attached to and extending normally from a rigid disc portion of larger diameter has been suggested. The rigid disc portion is subcutaneously implanted, with the cylindrical portion extending outside the patient. Typically, flexible catheter tubing is threaded through a hole extending along the central axis of the cylindrical and disc portions and then welded to the device. In use, the flexible catheter tubing extends into the body of a patient, thereby providing an indwelling catheter. Such a device has demonstrated excellent biocompatibility over periods of 6 to 28 months in several patients. A tight and sterile relationship between skin tissue and hydroxylapatite was observed. However, the design of that prior device implies severe restriction of patient mobility, partly because of the rigid cylindrical portion extending essentially perpendicularly from the patient.